Valves can be actuated with various types of rotatable handles, such as a round handle, T-shaped handle or a handle with several spokes, to an open position, closed position or a throttled position between open and closed as selected to control the flow of materials through a pipeline. A valve sometimes must be maintained in a fully open position in order to achieve the desired flow through a pipeline. Also, a valve often must be adjusted to a throttled position (i.e. between open and closed) in order to achieve a selected rate of flow of materials through a pipeline. Further, however, it may be necessary to maintain a valve in a fully closed position so as to stop the flow of materials through a pipeline. An example of the latter case is the need to fluid carried in a pipeline such as a hydraulic line or compressed air line when maintenance or service work is to be performed. Each of these situations presents a need for a device that can be employed to assist in maintaining the rotatable handle of a valve in a selected position, and it would be desirable that any such device be capable of accommodating a valve handle in either an open, closed or throttled position.
In addition, it also would be desirable for any device of the foregoing type to include provision for accepting a lock so that the valve handle would be actuated to a changed position only upon appropriate authorization. For example, the Occupational Safety and Health Administration (OSHA) standard relating to safety requirements for the control of hazardous energy, 29 CFR .sctn.1910.147, entitled Control of Hazardous Energy Sources (Lockout/Tagout), establishes procedures to disable machinery or equipment and prevent the release of potentially hazardous energy while maintenance and servicing activities are performed. The standard requires, inter alia, that an energy source having a line valve that is capable of being locked out must be locked out to insure that equipment being controlled cannot be operated until the lockout is removed. A lockout is defined in the regulation as a positive means such as a lock to hold an energy isolating device in the safe position and prevent energizing of machinery or equipment. The regulation is applicable to any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal or other energy. The above OSHA regulation will now require, for example, that a valve installed on a pipeline carrying an energy source to machinery or equipment must include some form of device so that the valve can be locked in the closed position during maintenance or service.
Further, there is a need for a device of the foregoing type that can be retrofitted to existing valves so as to obviate the expense of replacing the many valves now in service with new valves that may include a builtin feature capable of maintaining a valve handle in one or more positions.
Guards for valve handles are described in the following U.S. patents:
280,912, Connolly, July 10, 1883; PA1 725,260, Speer, Apr. 14, 1903; PA1 3,980,099, Youngblood, Sept. 14, 1976; and PA1 4,516,414, Woolvin, May 14, 1985.
In addition, to the devices proposed by the patents, a valve guard has been sold by the assignee of this patent and other companies for use with valves having rotatable handles consisting of two molded plastic elements, each of a different structure, that are joined together by integral molded hinge elements. Our present invention relates to an improved guard for a valve handle that has utilitarian advantages not attainable by the above prior art devices.